Using tally marks, the required frequency is as given below:

The highest observation = 61.
The lowest observation = 17.
One of the class intervals = 40–48.
Class size = Upper class limit - Lower class limit = 48 – 40 = 8
∴ The appropriate classes can be:
16–24, 24–32, 32–40, 40–48, 48–56, 56–64
Thus, the frequency distribution table for the above data can be:

To represent the given data by a bar-graph, draw two axes perpendicular to each other. Now, represent ‘Months’ on OX and ‘Number of watch sold’ on OY. Erect rectangles of the same width. The heights of the rectangles are proportional to number of watches, using a suitable scale:

Here, scale is 1 cm = 500 watches
Since 500 watches = 1 cm
1000 watches = 2 cm
1500 watches = 3 cm
2000 watches = 4 cm
2500 watches = 5 cm

Since, a comparison of two activities (walking and cycling) is to be represented, therefore a double-graph is drawn by taking the schools along x-axis and number of children along y-axis, using a scale of 1 cm = 5 children.